Different motors with the same nominal horsepower may have different start current, torque curves, speeds and other variables. When selection a particular motor for an intended task all engineering parameters must be taken into account.

The four NEMA (National Electrical Manufacturers Association) designs have unique speed-torque-slip relationships - making them suited for different type of applications.

NEMA design A

maximum 5% slip

high to medium starting current

normal locked rotor torque

normal breakdown torque

suited for a broad variety of applications - like fans and pumps

NEMA design B

maximum 5% slip

low starting current

high locked rotor torque

normal breakdown torque

suited for a broad variety of applications, normal starting torque - common in HVAC application with fans, blowers and pumps

NEMA design C

maximum 5% slip

low starting current

high locked rotor torque

normal breakdown torque

suited for equipment with high inertia starts - like positive displacement pumps

NEMA design D

maximum 5-13% slip

low starting current

very high locked rotor torque

suited for equipment with very high inertia starts - like cranes, hoists etc.